Pressure Drop in Condensers

[jsainz]

I want to design a shell and tube condenser for steam coming out from a thin film evaporator at 1 Atm. What considerations must be taken regarding steam extractors to ensure that all the steam coming from the evaporator is condensed (pressure drop at the condenser, cooling agents...)?

 

[Torricelli]

companies offering steam ejectors (vacuum pumps) also offer condensers. Their design is very accurate as the pressure drop is critical for interstage condensers.
A directory of condenser manufacturers is available under

http://www.vacuum-guide.com

Hope it helps.

 

[Torricelli]

The steam ejectors (vacuum pumps) suppliers also offer condensers. Their design is very accurate as the pressure drop is critical for interstage condensers.
A directory of condenser manufacturers is available under

http://www.vacuum-guide.com

Hope it helps.

 

[hduncan]

if you want to make sure that all of the steam is condensed, then you will need to use a trap. with atmospheric pressure, this can be done by using a bucket trap and giving it sufficient hydrostatic head to let it operate. if you know that your always going to be at atmospheric pressure, then you could simply use a regular trap. this would ensure that all of the steam is condensed. water can be used on she tube side to condense the steam. sizing depends on the steam flow requirments.

 

[MJCronin]

jsainz,

It sounds like you are looking for a complete "steam surface condenser" equipped with ejectors/vacuum pump system, hotwell, level indication etc. This system would be similar to what you would find beneath a condensing steam turbine.

Each system is custom designed for the expected load

A good place to start would be to contact the people at Graham (

http://www.graham-mfg.com

) they have a small library of article about process steam condensers.

How much steam, what is your cooling source, operating pressures etc are all questions that must be answered. Corrosive cooling water can easilly double the condenser price........(you are not going to use seawater for cooling....are you ?....gulp...)

Come back with more details and we can make more suggestions.....

MJC

 

[jsainz]

The energy and mass balances are clear for me to condense the steam coming out from the evaporator (1000 Kg / hr), the fact is that I want to cool the steam with the same juice (similar to sugar solutions at 5 Brix) that i am going to concentrate after, just as a preheater (the juice enters at 30 degrees Celcius). I think that considering only a raise of 15 Degrees for this juice in the condensor is reasonable to avoid Calcium precipitates. Any way , I have another stream in the process that can be used to condense the steam and is just water at 30 C. My main woories are at the relation between the condenser and the steam extractor from the evaporator. I have to find a relation there to ensure all the stream is extracted from the evaporator and that the extractor can meet the pressure drop at the condenser. (Which extractor is recommended, any bleed for steam at the condenser, traps...) WHat do you think of a shell and tube condenser for this job?

Thanks for all the advices.
Javier

 

[ChuckEasley]

As long as you provide sufficient cooling to absorb the latent heat and some small amount of subcooling of the steam condensate, all of the steam will naturally flow into the condenser from the evaporator. A shell and tube condenser should work fine for this purpose. Normally you would condense on the outside of the tubes. The size of the condenser is set by the heat transfer requirements, and the resulting pressure drop will be quite small, less than 1 psi. If your evaporator can handle this back pressure, then you will not require any ejector to pull the steam out. Most exchanger fabricators will be able to give you an accurate calculation of the pressure drop. A book by Kern, "Process Heat Transfer" gives equations and good examples for estimating the condenser size and pressure drop.

 

[rmw]

go to

http://www.heatexchange.org

and find the steam surface condenser rating program for 60 USD and order it. It is real good, and inexpensive. They also have stds for barometrics which are used in sugarmaking too, because of the carryover of sugar particles.

RMW